1. Field of the Invention
The present invention relates to a data processing system, and particularly to a data processing system effective for the cases that include terminal equipment having a program of high importance dealing with secret information, such as an on-line system in a banking organ.
2. Prior Art
Secracy in an on-line system can be improved by a system in which, for example a central processing unit detects an unwarrantable terminal that is connected, and logically inhibits the communications between the unwarrantable terminal and the central processing unit. A concrete means can be represented by a system disclosed, for example, in Japanese Patent Laid-Open No. 137957.
According to the technique disclosed in the above publication, the diagnosis processing program in the central processing unit sends a microprogram for diagnozing terminal equipment to terminal equipment which executes a calculation with the hardware that constitutes the terminal equipment as a parameter and sends the result back to the central processing unit. The central processing unit then compares the result with a fixed value that has been stored in the central processing unit to thereby determine if the above terminal equipment is warrantable or not. When it is determined that the terminal equipment is not warrantable, communication is interrupted relative to the central processing unit.
Therefore, whether the terminal equipment equipped with constituent element (hardware) permitted as a system is warrantable or not, can be automatically and easily detected by the central processing unit without relying upon the operation.
In the above-mentioned system, however, no consideration has been given to cope with the operation by the forged program or unwarranted program in the terminal equipment. The microprogram (operation program) for diagnosis is sent from the central processing unit. Therefore, if the constituent element only of the terminal equipment is brought into agreement with a warrantable terminal equipment, the communication is made possible relative to the terminal equipment even though the program may have been forged therein.
According to the above-mentioned system, furthermore, a method which compares the calculated result from the terminal equipment with a fixed value prepared in advance in the central processing unit is employed in the central processing unit as means for detecting the warrant of the terminal equipment. Therefore, the communication could be easily made possible relative to the central processing if a person learns by eavesdropping a warrantable fixed value from a warrantable terminal equipment and if he forges a program to forge the warrantable terminal equipment to send the warrantable fixed value to the central processing unit.